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What is MdDS?

MdDS is considered to be a rare neurological condition (orphanet number 210272).  It is also known as Disembarkation Syndrome because it is often triggered after exposure to motion by ship, plane, train or car.  MdDS can also occur after using running machines or even from watching video games.  Non motion triggered MdDS can result from operations, injuries or for no easily identifiable reason.


Symptoms vary but often include a sensation of persistent rocking, bobbing or swaying.  This can be accompanied by cognitive impairments which include memory problems, problems with speech and difficulty with multi-tasking or following instructions (see papers on cognitive/vestibular interactions for further information).  People with MdDS may also have 

headaches or ‘silent’ migraines and nausea.  Additional symptoms can include the sensation of walking on a trampoline, problems with spatial co-ordination and loss of fine motor skills.  Many people experience severe physical exhaustion as a result of having MdDS.  


There are many physical and environmental factors that can alter the severity of symptom levels including hormone fluctuations, changes in the weather, exposure to certain audio frequencies and lux level changes or flickering lighting.  Enclosed and/or wide open spaces can cause symptom hikes and both bland and busy visual environments may also affect 

symptom levels.  Many people with MdDS find that the rocking symptoms abate when they are back in motion although symptoms may return more severely upon subsequent disembarkation.


Some people experience episodic MdDS with either short or long periods of remission.  For others the condition is continuous from onset or may become continuous as the condition progresses.  Symptom severity can vary from day to day or even hourly, which can make this a challenging condition to live with.  Initially MdDS was thought to mainly be triggered in women in their 40s and 50s.  However as the condition has gained recognition, more men have been diagnosed and the age range at onset is seen to be far more variable.  There is also a general understanding that no single factor can account for onset of MdDS, which is why one of the lead researchers calls it ‘the perfect storm’.  Factors from our previous medical histories are likely to play a part but there has been no research into the commonalities.


Despite increased recognition, people with MdDS often experience long delays when seeking a diagnosis and often pick up several unhelpful misdiagnoses along the way.  This can all have a profoundly negative psychological impact.  As patients with this condition often struggle either to work or to claim health benefits, the psychological fall-out from developing this condition should not be underestimated.  Unfortunately some clinicians put the cart before the horse and see the situational anxiety and depression that can result from onset – and delayed diagnosis - as the cause.  


Research into MdDS has been limited although more scientists, researchers and clinicians are taking an interest now.  Various theories have been proposed regarding the mechanisms of MdDS and, as a result, two treatment protocols have been developed.  One theory is that MdDS involves changes in neural connectivity which can be mediated via cranial 

stimulation.  Another theory is that the vestibulo-ocular reflex is affected and this has resulted in the opto-kinetic stimulation treatment.  At the time of writing neither of these treatments is available in the UK.  However we hope this situation will change soon.  A UK clinician has received world-class training in the opto-kinetic treatment and I am working with the clinical commissioning groups with respect to the cranial stimulation treatment.


One of the difficulties with MdDS is that it is hard to categorise.  Some clinicians see it as a form of Dysautonomia but that doesn’t help with accessing treatment.  Some see it as a form of ataxia and others make 

comparisons with concussion and/or sensory processing conditions.  Dr Hain views it as a motion-sickness variant.  With respect to motion triggered MdDS some vestibular neurologists have mentioned oscillations in neural pathways that can continue long after the original oscillation stimuli.  


Like most rare conditions MdDS is a complex, multi-system condition which can be very debilitating.  Most rare conditions carry a genetic component and further research is needed to establish biomarkers.  Historically in the UK treatment has been limited to vestibular physiotherapy which can help or harm and to ‘lifestyle changes’, which are often unavoidable anyway.  I hope that with the new approach of ‘Technology, Training, Treatment’ services for people with MdDS in the UK will improve.


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